High speed mechanical r-f waveguide switch



Aug. 25,1959 L. A. MEADOWS 2,901,703

HIGH SPEED MECHANICAL R-F WAVEGUIDE SWITCH Filed April 8, 1955' 2 Sheets-Sheet l 7300 RPM 'ROTOR SPEED v VSWR REF L45 ANGULAR DISPLACEMENT 4.92

"2.5 sec-F IN VEN TOR.

LEE A. MEADOWS Z I ATTORNEYS g- 1959v V L. A. MEADOWS 2,901,708

HIGH SPEED MECHANICAL R-F WAVEGUIDE SWITCH Filed. April 8, 1955 2 Sheets-Sheet 2 Fig. 2

JNVE R. LEE A MEADOW A r TORNE xs United States Patent HIGH SPEED MECHANICAL R-F WAVEGUIDE SWITCH The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the pay-- ment of any royalties thereon or therefor.

This invention relates to RF Waveguide switches and more particularly to a single-pole, five-throw switch of a mechanical, concentric rotor-stator type, with both electrical and mechanical symmetry.

This switch is capable of switching 250 kw. (peak RF) at a pole-to-pole repetition rate of 1825 times per second. Previously used gas and ferrite switches capable of this performance do not have long enough useful life to be practical. A single-pole, six-throw switch, with rotating discs and asymetrical series, take-off type transmission lines, has also been used. Apertures in these discs are used to select the take-ofi point along the transmission line and in this manner provide commutation of the input to the outputs. However, this switch requires the construction of flat thin discs of 7-inch diameter for operation at speeds over 8000 r.p.m., which presents mechanical construction and maintenance problems. On-time of the switch is proportional to the disc diameter, the ratio of on-time to ofi-time increasing with switch size. Mechanical tolerances must be small and the asymmetrical configuration of the transmission line makes them difficult to obtain and hold. constructional errors are accumulative. Furthermore, the series trans mission line greatly impairs the bandwidth and makes electrical symmetry of the switch impossible because of the different lengths of shorted waveguide stub for each output. Electrical symmetry is desirable so that unequal pulling of the transmitter magnetron from pulse to pulse will not occur when the magnetron is operating off the design frequency of the switch.

These faults have been eliminated by the use of a symmetrical three-leg rotor and a concentric five-aperture stator mechanical switch comprising this invention. This switch has both electrical and mechanical symmetry, has five times the bandwidth of the series take-ofi type switch, and is very rugged mechanically as compared to the disc type switch. The on-time of this switch is inversely proportional to the rotor diameter, which provides for a physically smaller switch for a given on-time. Three on-times per output per pole per revolution of the rotor is provided, permitting the switching of energy at the rate of 1825 poles per second. The insertion loss is less than .1 db.

An object of this invention is the provision of an improved waveguide switch having electrical and mechanical symmetry.

Another object is the provision of a waveguide switch of a high speed, high power mechanical type having a wide bandwidth and small insertion loss.

Another object is the provision of a rotor-stator wave guide switch in which the on-time of the switch is inversely proportional to the rotor diameter.

Another object is the provision of a waveguide switch 2 which is simple to fabricate, easy to maintain, yet is rugged and dependable in'service.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understod by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 shows the disassembled parts of the switch;

Fig. 2 is a diagram showing the relative position of the rotor and stator from output to output;

Fig. 3 shows the input transition with parts broken away to show the interior; and

Fig. 4 is a plot of typical VSWR and amplitude vs. relative angle of rotor and stator.

Referring now to the drawings in which the like numerals designate like parts in each of the several views, there is shown in Fig. 1 the rotor 10, stator 11, input transition 12, drive motor 13, and cover plate 14 which, together with the synchronizer pickup which is not shown, comprise the waveguide switch. The rotor 10 is an aluminum drum with three .400 x .900 inch waveguides 15 machined radially to its center and equally spaced about the periphery thereof. These 'waveguides have rectangular chokes 16 at the rotor periphery. Excitation of the three legs is obtained by a mutually perpendicular circular waveguide 17 on the rotor axis with a resonant ring mode filter 18 and matching iris. A flange 19 on one end of the rotor contains 15 Hipersil inserts 20 for the purpose of synchronizing the transmitter with the switch, said inserts 20 may be made of any magnetic metal alloy but preferably of the metal known in the trade as Hipersil.

The stator 11 is an aluminum cup with five .400 x .900 inch apertures 21. The apertures-are machined so their axes fall on radial lines 72 degrees apart and in a plane perpendicular to the stator axis shown also in Fig. 2. Machined flats with holes tapped to accept a choke flange are provided at the stator periphery for each output.

Transition 12, best shown in Fig. 3, including a strut supported resonant ring 22 and incorporating a choke sec tion 23 for the rotary joint between the rotor and stator is used to couple the switch input from an energy source (not shown) to the rotor.

Two pickup coils 26 and their associated permanent magnet 28 comprise the synchronizer pickup and are mounted on the cover plate 14 in openings 24 therein. The synchronizer may be mounted in any suitable manner, such as for example, by potting in a casing 30 bolted to cover 14. These pickups generate sync pulses by virtue of the variation of the reluctance of the magnetic field caused by the Hipersil inserts in the rotor passing their pole pieces. These sync pulses are used to trigger the transmitter during the on-period and also to identify output number 1, three of inserts 20 being deeper than the others to establish a reference for output No. 1 by virtue of the angular position of the pickup coils on the cover plate 14 with respect to output aperture 1 (Fig. 2) on stator 11.

An aircraft type volt, 3 phase,'400 cycle, 7300 rpm. A horsepower, totally enclosed drive motor 13 is coupled via a nylon coupling (not shown) to the rotor 10.

The sequence of operation for this switch starting with output No. 1 is as follows:

(1) The RF. pulse from the transmitter is initiated by a signal from the synchronizer pickup, entersthe switch through the input transition 12 and then passes down the circular, waveguide 17 to the rotor legs 15 to simultaneously effect shunt excitation of all three legs, At this time one leg of the rotor is 2.46 degrees ahead ofstator aperture 1 as shown by the solid centerlines in, the first diagram in Fig; 2. Since the remaining two rotor legslare short circuitedby the stator wall the R.F.

(2) Commutation fromoutput one to two takes place from a rotor position of 2.46 degrees beyond output 1 to 2.46 degrees before output two, at which time the switch is again ready to pass R.F. energy and trigger the source. Commutation from output to output occurs every 24 degrees of rotation to produce 15 switches per revolution. Thus at 7300 r.p.m., 1825 switches per second is achieved. A reduction of the rotor shaft speed by a factor of two will have the effect of doubling the on-time while halving the repetition frequency.

The energysource, which forms no part of this invention, may be, for example, a conventional modulated magnetron which is internally timed to produce one or more pulses for a predetermined time and which is externally triggered by a signal from the synchronizer pickup. Preferably the energy source has its internal timing set to terminate the generation of energy to be transmitted at or before the end of each on-time period of the switch. This may be simply done by pre-setting the internally timed period of energization of the source for a period of time which is less than the on-time of the switch (4.92 degrees in the above example). Thus, while the energy from the source is initiated at the initiation of each on-time period, this energy flow is terminated by the source itself before the end of the on-time period.

While many other modifications at once become apparent to those skilled in theart, the following are exemplary of those most obvious:

1) More or less than five poles may be obtained by changing the number of Waveguide legs in the rotor and the number of apertures in the stator. The rotor legs may also be staggered in different planes perpendicular to the rotor axis thus providing additional rotor legs.

(2) Samller size may be obtained by utilizing dielectric filled waveguides in place of the standard waveguide sizes used.

(3) Circular waveguides substituted for the rectangular waveguides in the rotor and stator may simplify fabrication of these components.

(4) Die casting or electro-forming methods may be used for quantity fabrication.

(5) If the stator and rotor waveguides are made unequal in size the amplitude variation for a given on-time may be made substantially. flat.

Obviously many other modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that Within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Whatisclaimedis:v H

l. A waveguide switch comprising a rotor of three waveguide transmission paths A, B, C, a stator having fiveopenings, 1 to 5, said paths and openings are respectively equispaced about the peripheries of said rotor .and sa d stator respectively such that alignment of any path with any opening precludes-alignment of any other path with any other opening whereby energy is transmitted through said paths to said openings in the following sequential order: A to l, B to 2, C to 3, A to 4,:

Bto 5,Cto 1,Ato2,Bto3,Cto4,Ato5,Btol, Cto2,Ato3,Bto4andCto5.

2. The R-F switch as in claim 1, each said path and opening being aligned during a predetermined period sufficient to provide an amplitude variation of no more than .1 db during on-time transmission.

3. A waveguide switch comprising a rotor having a plurality of waveguide paths extending radially from its center and terminating at equally spaced points about the periphery thereof, a circular waveguide on the axis of said rotor and mutually perpendicular to said paths for excitation of said paths, a stator having a plurality of apertures in equally spaced relationship in a plane perpendicular to the stator axis, the number of said apertures being greater than the number of said paths, a transition forming a rotary joint with said circular waveguide on said rotor for coupling the switch input to said rotor, and means for driving said rotor.

4. A waveguide switch comprising a rotor having three Waveguide paths extending radially from its center and terminating at equally spaced points about the periphery thereof, a circular waveguide on the axis of said rotor and mutually perpendicular to said paths for excitation of said paths, said circular waveguide including a resonant ring mode filter and matching iris, a stator having a plurality of apertures greater in number than said paths and in equally spaced relationship in a planeperpendicular to the stator axis, a transition including a choke section adjacent to and forming a rotary joint with said circular waveguide on said rotor for coupling the switch input to said rotor, and means for driving said rotor.

5. A waveguide switch comprising a rotor with three waveguide paths extending radially from its center and terminating at equally spaced points about the periphery thereof, said paths having'chokes on each side of their periphery openings, a mutually perpendicular circular waveguide on the axis of said rotor for excitation of said paths, said circular waveguide including a resonant ring mode filter and matching iris, said rotor having a flange at one end thereof having a plurality of magnetic metal alloy inserts thereon for use in synchronizing energy pulses with predetermined rotational positions of said rotor, a stator having a plurality of apertures in equally spaced relationship in a plane perpendicular to the stator axis, a transition includinga strut supported resonant ring and a choke section adjacent to and forming a rotary joint with said circular waveguide on said rotor for coupling the switch input to said rotor, and a motor driving said rotor.

6. A waveguide switch comprising a rotor with three waveguide paths extending radially from its center and terminating .at equally spaced points about the periphery thereof, said paths having chokes on each side of their periphery openings, a mutually perpendicular circular waveguide on the axis of said rotor for excitation of said paths, said circular waveguide including a resonant ring mode filter and matching iris, said rotor having a flange at one end thereof having a plurality of magnetic metal alloy inserts thereon for use in synchronizing energy pulses withpredetermined rotational positions of said 'rotor, a stator having a plurality of apertures in equally coupling the switch input to said rotor, a cover plate for said stator for enclosing said rotor, said transition being mounted on said cover plate, and means for driving said rotor. 1

7.--A Waveguideswitch comprising a stator having openings, a rotor having waveguide transmission paths alignable with said openings whereby energy may be transmitted therethrough, said stator having a cover plate mounting magnetic synchronizing means thereon, said rotor having slots with magnetic metal alloy inserts therein thereby to vary the reluctance of the magnetic field about said cover plate as the rotor revolves about its axis, said slots and said inserts being so spaced on said rotor as to externally indicate the position of one of said paths.

8. A waveguide switch comprising a stator having equally spaced openings about the periphery thereof, a rotor mounted for rotation within said stator and having waveguide paths alignable with said openings whereby energy may be transmitted therethrough, a transition for coupling said rotor to an energy source, a cover plate for said stator for enclosing said rotor, reluctance sensitive means on said plate, said transition being mounted on said cover plate, and synchronizing means on said rotor cooperating with said reluctance sensitive means for varying the reluctance thereof to indicate the position of one of said waveguide paths.

9. The apparatus in claim 8 in which the rotor synchronizing means comprises a flange on said rotor with a plurality of slots spaced about the periphery thereof, magnetic metal alloy inserts mounted within said slots, said means varying the reluctance about a point on said cover plate as the rotor revolves.

10. A high speed radio frequency energy switch comprising a rotor having a plurality of energy transmission paths extending radially from its center, means for simultaneously efi'ecting shunt excitation of said paths, a stator extending around said rotor, said stator having a number of apertures therein greater than the number of said paths, whereby energy may be transmitted through an aperture substantially aligned with one of said paths and the stator short circuits the energy in those paths not substantially aligned with an aperture.

11. The switch of claim 10 wherein said paths and apertures are respectively equi-spaced about the peripheries of said rotor and said stator respectively such that alignment of any path with any aperture precludes alignment of any other path with any other aperture.

'12. A high speed waveguide switch comprising a rotor having a waveguide section extending axial-1y thereof, said rotor including a plurality of waveguide paths extending radially from said section and terminating at equally spaced points about the periphery of said rotor, a stator surrounding said rotor and having a plurality of apertures therein which are :alignable with the terminations of said paths, the number of said apertures being greater than the number of said paths, and means for driving said rotor to eifect successive alignment of different ones of said paths with diiferent ones of said aperture.

13. The switch of claim 12 including cooperating means on said rotor and stator for producing a trigger signal synchronized with the rotation of said rotor.

References Cited in the file of this patent UNITED STATES PATENTS 2,423,130 Tyrrell July 1, 1947 2,519,750 Ehlers Aug. 22, 1950 2,563,990 Cutler Aug. 14, 1951 2,705,776 Starr Apr. 5, 1955 FOREIGN PATENTS 201,753 Germany Sept. 15, 1908 

